Our P01 research is based on the hypothesis that dose escalation with improved radiotherapy methods will enhance local tumor control, improve survival and decrease normal tissue toxicity. Clinical evidence has shown that improvement provided by 3DCRT and IMRT can minimize normal tissue irradiation, permit increase in prescription dose and improve the local control of prostate cancer. Further improvement are being proposed in this PO1 so that similar clinical advance can be achieved in other disease sites, particularly for NSCLC and H/N patients. Another significant component of our theme is the investigation of the application of biological imaging to IMRT. There are three research projects (RP). The overall goal of RP1 Is to use IMRT to improve nasopharynx. The first aim is to examine whether dose in a randomized Phase III study, comparing the adjuvant androgen deprivation and 75.6 Gy IMRT, in conduct a phase ll study in carcinoma of the nasopharynx using IMRT to deliver a ?concurrent? boost for biological dose escalation and to assess if the benefit. Another task is the analysis and modeling of clinical outcome. This continues the successful ongoing effort but promises to be even more fruitful given the increasing body and the maturation of outcome data. In RP2, advance in several areas are joint in the treatment of NSCLC: FDG-PET for improved GTV delineation, respiratory-correlated image acquisition in PET/CT for accurate PTV definition, inverse planning and respiration-gated IMRT for conformal dose distribution, dose escalation guided by radiobiological consideration, and the development of mega-voltage cone-beam CT for treatment verification. These provide unprecedented accuracy to test the hypothesis that NSCLC can be locally controlled with high dose radiotherapy. The focus of RP3 is treatment uncertainty. The first major task is to develop methods of more accurately determine the delivered dose to tumor regions detected by magnetic resonance spectroscopic imaging (MRSI) in the prostate. The second task is to develop and implement on-line intervention to reduce uncertainty and improve dose conformality in the treatment of prostate, by acquiring CT scans and applying daily corrections prior to treatment, and to assess its efficacy. Third, for NSCLC patients we shall develop respiration-correlated spiral CT (RCCT) to study tumor motion and to determine the optimal respiratory phase for gated (RG) IMRT. Lastly, we shall design a strategy to reduce GTV deviation due to respiration-induced variations, using MV cone-beam CT imaging (MVCBI).